The purpose of the proposed research is to assess the effects of early exposure to diethylstilbestrol (DES) and 19 nor ethyl testosterone (19-NET) on humans and animals. The assessment in humans who were exposed to DES or to 19-NET during prenatal development will include indices of cognitive abilities, personality/temperament, and behavior. Mice will be administered DES or 19-NET prenatally, postnatally, or pre and postnatally (a regimen mimicking human exposure) and studied for the effects on reproductive physiology, sex behavior, aggression, parental behavior, activity, and avoidance learning.